Long-term memory helps chimpanzees in their search for food

October 23, 2013
This is an image of an adult female chimpanzee inspecting a food tree. Credit: MPI f. Evolutionary Anthropology/K. Janmaat

Where do you go when the fruits in your favorite food tree are gone and you don't know which other tree has produced new fruit yet? An international team of researchers, led by Karline Janmaat from the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, studied whether chimpanzees aim their travel to particular rainforest trees to check for fruit and how they increase their chances of discovering bountiful fruit crops. The scientists found that chimpanzees use long-term memory of the size and location of fruit trees and remember feeding experiences from previous seasons using a memory window which can be two months to three years ago.

For their study, the researchers recorded the behavior of five chimpanzee females for continuous periods of four to eight weeks, totaling 275 complete days, throughout multiple fruiting seasons in the Taï National Park, Côte d'Ivoire. They found that chimpanzees fed on significantly larger than other reproductively mature trees of the same species, especially if their fruits emitted an obvious smell. Interestingly, trees that were merely checked for edible fruit, but where monitoring could not have been triggered by smell, or the sound of fallen fruit, because the trees did not carry fruit, were also larger.

The researchers found that chimpanzees checked most trees along the way during travel, but 13% were approached in a goal-directed manner. These targeted approaches were unlikely initiated by visual cues and occurred more often when females foraged alone and when trees were large as opposed to small. The results suggested that their monitoring was guided by a long-term "what-where" memory of the location of large potential food trees. For their results, researchers analysed which of nearly 16000 potential food trees with different crown sizes were actually approached by the chimpanzees.

Observations on one female, followed intensively over three consecutive summers, suggested that she was able to remember feeding experiences across fruiting seasons. Long-term phenological data on individual trees indicated that the interval between successive fruiting seasons, and hence the minimal "memory window" of chimpanzees required for effective monitoring activities, could vary from two months to three years.

"The present study on chimpanzees is the first to show that our close relatives use long-term during their search for newly produced tropical , and remember feeding experiences long after trees have been emptied", says Karline Janmaat of the Max Planck Institute for Evolutionary Anthropology.

"For a long time people claimed that animals, contrary to humans, cannot remember the past. This study helps us to understand why and other primates should remember events over long periods in time. And guess what? It also shows they do!" says Christophe Boesch of the Max Planck Institute for Evolutionary Anthropology.

Explore further: Chimpanzees use botanical skills to discover fruit

More information: Karline R. L. Janmaat, Simone D. Ban, Christophe Boesch. Chimpanzees use long-term spatial memory to monitor large fruit trees and remember feeding experiences across seasons. Animal Behavior, October 23, 2013.

Related Stories

Chimpanzees use botanical skills to discover fruit

April 10, 2013

(Phys.org) —Fruit-eating animals are known to use their spatial memory to relocate fruit, yet, it is unclear how they manage to find fruit in the first place. Researchers of the Max Planck Institute for Evolutionary Anthropology ...

In chimpanzees, hunting and meat-eating is a man's business

March 26, 2013

(Phys.org) —Observations of hunting and meat eating in our closest living relatives, chimpanzees, suggest that regular inclusion of meat in the diet is not a characteristic unique to Homo. Wild chimpanzees are known to ...

Fighting back against citrus greening

January 25, 2013

U.S. Department of Agriculture (USDA) scientists in Fort Pierce, Fla. are helping citrus growers and juice processors address the threat posed by Huanglongbing (HLB), a disease that is costing the citrus industry millions ...

Hunting for meat impacts on rainforest

March 20, 2013

Hunting for meat in the African rainforests has halved the number of primates. However, the hunting also has other negative consequences. The decline in the number of primates causes a reduction in the dispersal of seed by ...

Recommended for you

Knowledge gap on the origin of sex

May 26, 2017

There are significant gaps in our knowledge on the evolution of sex, according to a research review on sex chromosomes from Lund University in Sweden. Even after more than a century of study, researchers do not know enough ...

The high cost of communication among social bees

May 26, 2017

(Phys.org)—Eusocial insects are predominantly dependent on chemosensory communication to coordinate social organization and define group membership. As the social complexity of a species increases, individual members require ...

Darwin was right: Females prefer sex with good listeners

May 26, 2017

Almost 150 years after Charles Darwin first proposed a little-known prediction from his theory of sexual selection, researchers have found that male moths with larger antennae are better at detecting female signals.

Why communication is vital—even among plants and funghi

May 26, 2017

Plant scientists at the University of Cambridge have found a plant protein indispensable for communication early in the formation of symbiosis - the mutually beneficial relationship between plants and fungi. Symbiosis significantly ...

1 comment

Adjust slider to filter visible comments by rank

Display comments: newest first

RobertKarlStonjek
1 / 5 (1) Oct 24, 2013
Recollection for facts, such as the location of food, is very different from the recollection of events.

It has been amply demonstrated in humans and related beautifully by Oliver Sacks that humans with complete amnesia can still respond to information learned from past experience even though they are totally unable to recall it.

For instance a joke buzzer on the hand of the doctor gives the patients a little shock when they shake hands. The next day, even though the patient can not recall who the doctor is or ever having met him (eg Sacks) the patient hesitates or refuses to shake hands.

This kind of learning does not require what we call 'episodic memory'. Chimps may or may not have long term episodic memory but the study does nothing to establish this.

Chimps that can communicate with sign language seem to quickly forget most if not all past events even though they acquire and retain information over a long period eg learning sign language.

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.